Why Does the Precautionary Principle Suffice for Blood Regulation?

Traditional approaches to blood regulation emphasise the precautionary principle and pursue zero-risk for viral transmission; these traditional approaches have usually followed tragedy, such as the HIV and hepatitis C infections that followed the use of factor VIII concentrates. However, a much more haphazard haemovigilance system operates for general adverse events. Such imprecise assessment of hazards prevents sound benefit-risk assessment, and for blood products this is further confounded by the fact that their efficacy has attracted little systematic study. The ongoing COVID-19 pandemic has now prompted the proposal of a convalescent plasma (CP) blood product. Clearly, mere freedom from infectious agents will not suffice in assessing CP, and an objective measure of efficacy, so as to permit formal benefit-risk analysis, is essential. This is both a scientific and an ethical demand, as has been the case for other experimental COVID-19 treatments. With special reference to COVID-19 CP, the well-recognized adverse events of transfusion-associated lung injury (TRALI) and transfusion-associated circulatory overload (TACO) will be important. Furthermore, not only efficacy but also product quality attributes (e.g., antibody titre) will have to be defined. Both of these are outside the traditional regulatory philosophy for blood products and are needed to truly assess the benefit-risk of this putative therapeutic product.